The present invention relates to apparatus for indicating a change in the control setting of an instrument, and more particularly to apparatus for indicating when an adjustment of the sensitivity and balance controls of a polygraph module has occurred.
Instruments for detecting and measuring physiological changes that accompany emotional stress are well-known under the commonly used term of lie detectors. Such instruments are also often called polygraphs, and generally consist of sensors physically connected to an individual's body for measuring various physiological parameters. Such sensors include a blood pressure cuff, a pair of respiration belts, and skin resistance finger electrodes, all suitably coupled to recording pens traversing a record chart. Examples of such instruments and polygraph measuring systems can be found in the following U.S. patents:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 1,472,016 Dressler Oct. 23, 1923 2,944,542 Barnette et al July 12, 1960 3,850,169 Gebben et al Nov. 26, 1974 3,915,156 Wastl et al Oct. 28, 1975 4,085,740 Allen, Jr. Apr. 25, 1978 4,178,918 Cornwell Dec. 18, 1979 4,442,845 Stephens Apr. 17, 1984 4,520,232 Wilson May 28, 1985 ______________________________________
In a polygraph machine, each of the above-noted physiological changes are typically coupled to recording pens by means of an electronic module that has both a sensitivity and balance (centering) control. Each control may be adjusted as desired by an examiner to change the amplitude and vertical position of the recording pens as they traverse a record chart. Oftentimes, an examiner will make such adjustments while an individual subject is under examination to provide a more accurate indication of the physiological changes occurring in response to any emotional stress developed by the subject.
It is therefore desirable to provide apparatus which may be connected to the polygraph modules that could detect if either the sensitivity or balance (centering) control has been adjusted, and display the detected adjustment on the polygraph record chart in such a way that the display would coincide on the chart, in time, with the moment the adjustment was made by the examiner. The purpose of such apparatus is at least two-fold. First, it would aid an examiner with an indication of where notes should be made on the record in order to describe the adjustment that was made. Secondly, it would prevent a change in balance (centering) or sensitivity from being forgotten by an examiner and being mistaken as a response.